A known configuration for a magnetless rotating electric machine with a rotor that does not use a permanent magnet includes a rotor having rotor salient poles wound with a rotor coil, wherein an induced current develops in the rotor coil from a field magnet originating from a stator and magnetizes the rotor salient poles.
In addition to the related-art method for winding the coil around the rotor salient poles in the magnetless motor, another method for winding a coil around a rotor yoke is disclosed in JP 2010-279165 A. Also disclosed is a configuration in which salient poles of a rotor are provided with an induction coil to be placed close to a gap between the rotor and the stators and a common coil which differs from the induction coil and which is to be placed away from the stators. Further disclosed is a configuration including the induction coil wound around the rotor salient poles and the common coil wound around a rotor core.
JP 2011-244643 A discloses a double-stator motor as a method relevant to the present disclosure. Circumferentially-magnetized permanent magnets are placed on an annular rotor. An inner stator is placed on the inside of the rotor, and an outer stator is placed on the outside of the rotor. Each of the inner and outer stators has a Y-connected three-phase coil. The inner stator and the outer stator have the same number of magnetic poles. Permanent magnets placed on the rotor supply magnetic flux in parallel to both the inner stator and the outer stator.
The magnetless rotating electric machine has a cost advantage by virtue of not using an expensive magnet material. However, the coil wound around the rotor salient poles may break away from the rotor salient poles by the centrifugal force stemming from rotation of the rotor. When a coil presser, or the like, is used to prevent the breakaway of the coil, a structure becomes complicated, which imposes a limitation on a space for winding the coil and deteriorates output efficiency of the rotating electric machine.
An object of the present disclosure is to provide a magnetless rotating electric machine in which the coil does not break away from the rotor salient poles. Another object is to provide a magnetless rotating electric machine capable of improving an output further while preventing the coil from breaking away from the rotor.